CN109283729B

CN109283729B - Light redirecting film

Info

Publication number: CN109283729B
Application number: CN201810018419.8A
Authority: CN
Inventors: 郭真宽; 洪群泰; 吴丰旭
Original assignee: BenQ Materials Corp
Current assignee: BenQ Materials Corp
Priority date: 2017-07-20
Filing date: 2018-01-09
Publication date: 2021-04-16
Anticipated expiration: 2038-01-09
Also published as: CN109283729A; TWI645218B; TW201908774A

Abstract

The invention provides a sandwich flat-plate-shaped light redirecting film, which comprises a first layer; a second layer; and an intermediate layer sandwiched between the first layer and the second layer, the intermediate layer including a first grating surface having a plurality of first gratings extending in a first direction and a second grating surface having a plurality of second gratings extending in a second direction, and an angle at which the first direction intersects the second direction is between 90 ° ± 10 °; the first grating surface of the intermediate layer is filled and planarized by the first layer, and the second grating surface of the intermediate layer is filled and planarized by the second layer.

Description

Light redirecting film

Technical Field

The present invention relates to a light redirecting film, and more particularly, to a light redirecting film that improves the optical efficiency of a display at wide viewing angles, such as contrast, color saturation, and color accuracy.

Background

The liquid crystal display with the characteristics of high contrast, no gray scale inversion, micro color cast, high brightness, rich colors, high color saturation, fast response speed, wide viewing angle and the like is an adjusting material which has high-efficiency refractive index and is widely used for the display in the current market trend, but liquid crystal molecules have different symmetries at different viewing angles, so that vertical light and oblique light have different paths when passing through a liquid crystal layer of the display. Therefore, a general display, such as a liquid crystal display (lcd) or an organic light emitting diode (oled) display, is particularly prone to a white (color) or gray-scale inversion (gray-scale inversion) phenomenon at a wide viewing angle, resulting in a low contrast or abnormal color expression of an image.

Several methods have been proposed to improve the above-mentioned disadvantages, such as using a Twisted Nematic (TN) liquid crystal display in combination with a wide viewing angle film to equalize the central viewing angle and the image at the wide viewing angle; a wide-viewing-angle (MVA) display is used, or a diffusion film or a diffraction film is attached to the surface of the display.

However, a wide viewing angle film for a Twisted Nematic (TN) liquid crystal display is expensive; the wide-viewing angle display has complex manufacturing process, low yield and high cost; the diffusion film is not easy to accurately control the light rays emitted from the display at different angles; the diffraction film is not easy to control the optical paths with different dimensions by a single diffraction structure layer.

Therefore, the present invention discloses a light redirecting film with a two-dimensional (2D) diffraction structure suitable for a display to avoid the phenomenon of color washout or gray-scale inversion (gray-scale inversion) of the display at a wide viewing angle and to improve the efficiency of the display.

Disclosure of Invention

It is another feature of the present invention to provide a light redirecting film as described above, wherein the first layer has a refractive index of n1, the intermediate layer has a refractive index of n2, and the second layer has a refractive index of n3, wherein n1, n2, and n3 are all between 1.4 and 1.7.

It is another feature of the present invention to provide a light redirecting film as described above and n2 is greater than n1 and n2 is greater than n 3.

It is a further feature of the present invention to provide a light redirecting film as described above and n1 is the same as or different from n 3.

It is still another feature of the present invention to provide a light redirecting film as described above and having a difference between n2 and n1 of not less than 0.1 and not more than 0.3.

It is still another feature of the present invention to provide a light redirecting film as described above and having a difference between n2 and n3 of not less than 0.1 and not more than 0.3.

It is still another feature of the present invention to provide a light redirecting film as described above, wherein each of the first gratings has a width w1, each of the second gratings has a width w2, and each of w1 and w2 is independently between 0.3 μm and 1.5 μm.

It is still another feature of the present invention to provide a light redirecting film as described above, wherein each of the first gratings has a depth d1, each of the second gratings has a depth d2, and each of d1 and d2 is independently from 0.5 μm to 1.5 μm.

It is still another feature of the present invention to provide a light redirecting film as described above, wherein a spacing between two adjacent first gratings is g1, a spacing between two adjacent second gratings is g2, and g1 and g2 are each independently between 0.3 μm and 1.5 μm.

It is still another feature of the present invention to provide a light redirecting film as described above, wherein the width and depth of each of the first gratings and each of the second gratings, the distance between two adjacent first gratings, and the distance between two adjacent second gratings may be the same or different

It is still another feature of the present invention to provide a light redirecting film as described above, further comprising an optical film adhered to the light redirecting film, wherein the optical film is selected from one or a combination of a polarizing film, a hard coat film, a highly reflective film, an anti-glare film, and a protective film.

The above summary is intended to provide a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and is intended to neither identify key/critical elements of the embodiments nor delineate the scope of the embodiments. The basic spirit of the present invention and the technical means and embodiments adopted by the present invention will be easily understood by those skilled in the art after referring to the following embodiments.

Drawings

FIG. 1 is a perspective view of a light redirecting film according to a preferred embodiment of the present invention.

FIG. 2 is a perspective view of the first and second grating surfaces of the intermediate layer of the light redirecting film shown in FIG. 1.

Fig. 3 is a cross-sectional view taken in the direction D2 of the first grating surface on the intermediate layer as shown in fig. 2.

Fig. 4 is a cross-sectional view taken in the direction D1 of the first grating surface on the intermediate layer as shown in fig. 2.

FIG. 5 is a perspective view of a light redirecting film according to another preferred embodiment of the disclosure.

FIG. 6 is a perspective view of a light redirecting film according to yet another preferred embodiment of the present disclosure.

Detailed Description

In order to make the disclosure more complete and complete, the following description is given for illustrative purposes, with reference to embodiments and examples of the invention; it is not intended to be the only form in which the embodiments of the invention may be practiced or utilized. The embodiments disclosed below may be combined with or substituted for one another as desired, or additional embodiments may be added to the embodiments, without further recitation or description.

Examples

First, please refer to fig. 1-2. Fig. 1 is a perspective view of a light redirecting film 10 according to a preferred embodiment of the present invention, and as shown in fig. 1, the light redirecting film 10 is a sandwich plate structure. FIG. 2 is a perspective view of the first grating surface 14a and the second grating surface 14b of the intermediate layer 14 of the light redirecting film shown in FIG. 1. As shown in FIG. 1, the light redirecting film 10 includes a first layer 12, a second layer 16, and an intermediate layer 14 sandwiched between the first layer 12 and the second layer 16. As shown in fig. 2, the intermediate layer 14 includes a first grating layer 14a having a plurality of first gratings 141 extending in a first direction (D1), and a second grating layer 14b having a plurality of second gratings 142 extending in a second direction (D2), and the first direction (D1) intersects the second direction (D2) at an angle between 90 ° ± 10 °. In addition, as shown in fig. 1, the first grating surface 14a of the intermediate layer 14 is filled and planarized by the first layer 12, and the second grating surface 14b of the intermediate layer 14 is filled and planarized by the second layer 16.

According to one embodiment of the present invention, the refractive index of the first layer 12 is n1, the refractive index of the intermediate layer 14 is n2, the refractive index of the second layer 16 is n3, and n1, n2, n3 are all between 1.4 and 1.7. In addition, the material of the first layer 12, the intermediate layer 14, and the second layer 16 may be selected from a UV curable resin or a thermal curable resin, such as an acryl resin, a silicon resin, a urethane resin, an epoxy resin, or a combination thereof.

According to another embodiment of the invention n2 is greater than n1 and n2 is greater than n 3.

According to another embodiment of the present invention, n1 is the same as or different from n 3.

According to another embodiment of the present invention, the difference between n2 and n1 is not less than 0.1 and not more than 0.3.

According to another embodiment of the present invention, the difference between n2 and n3 is not less than 0.1 and not more than 0.3.

The size of the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b can be determined according to the design of different displays. Referring to fig. 2, 3 and 4, fig. 3 is a cross-sectional view taken along a direction D2 of the first grating surface 14a on the intermediate layer 14 shown in fig. 2. According to one embodiment of the present invention, each of the first gratings 141 illustrated in FIG. 3 has a width w1 between 0.3 μm and 1.5 μm, and preferably between 0.4 μm and 0.6 μm; its depth d1 is between 0.5 μm and 1.5 μm, and preferably between 0.7 μm and 1.3 μm; the spacing g1 between two adjacent first gratings 141 is between 0.3 μm and 1.5 μm, and preferably between 0.4 μm and 0.6 μm. In addition, the first gratings 141 on the first grating surface 14a may have the same or different sizes, and may be sequentially, periodically or randomly formed on the first grating surface 14a of the intermediate layer 14.

As shown in fig. 4, which is a cross-sectional view taken along the direction D1 of the second grating surface 14b on the intermediate layer 14 shown in fig. 2. According to one embodiment of the present invention, each of the second gratings 142 illustrated in FIG. 4 has a width w2 between 0.3 μm and 1.5 μm, and preferably between 0.4 μm and 0.6 μm; its depth d2 is between 0.5 μm and 1.5 μm, and preferably between 0.7 μm and 1.3 μm; the spacing g2 between two adjacent second gratings 142 is between 0.3 μm and 1.5 μm, and preferably between 0.4 μm and 0.6 μm. In addition, the second gratings 142 on the second grating surface 14b may have the same or different sizes, and may be sequentially, periodically or randomly formed on the second grating surface 14b of the intermediate layer 14.

The first grating surface 14a and the second grating surface 14b of the middle layer 14 can be used to improve the common phenomenon of color washout and gray-scale inversion (gray-scale inversion) of the panel at the horizontal viewing angle and the vertical viewing angle. In addition, the dimensions, such as the width, the height, and the pitch, of the first grating 141 and the second grating 142 can be set to be the same or different according to the requirements of different displays. According to an embodiment of the present invention, the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b have the same width, height and spacing. According to another embodiment of the present invention, the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b have different widths, heights and spacings.

The light emitted from each pixel on the panel (e.g., LCD) can pass through the first grating surface 14a and the second grating surface 14b, respectively, so that the light emitted from each pixel on the panel (e.g., LCD) can be redirected to a desired angle. In addition, compared with the light redirecting film formed by two sheet-shaped conventional diffraction layers, the single light redirecting film disclosed by the invention can omit the respective covering layers required by the conventional diffraction layers, and can simplify the design of using materials with different refractive indexes in different layers. In addition, the light redirecting film formed by integrating the stacked structure can reduce the interference caused by light passing through the display.

According to another embodiment of the present invention, the light redirecting film 10 may further be adhered to at least one optical film, such as a polarizing film, a hard coat film, a low reflection film, an anti-glare film, a protective film, etc., or directly to a display panel.

According to another embodiment of the present invention, the light redirecting film 10 is adhered to a polarizing film having an absorption axis (not shown) parallel to the first direction D1 extending from the first grating 141 or the second direction D2 extending from the second grating 142.

Referring to fig. 5, a perspective view of a light redirecting film according to another preferred embodiment of the present invention is shown. As shown in fig. 5, the polarizing film 18 including the first protective layer 181, the polarizing layer 182 and the second protective layer 183 is adhered to the second layer 16 of the light redirecting layer 10 by the first protective layer 181. According to another embodiment of the present invention, the polarizing film 18 can also be adhered to an adhesive layer (not shown) on the second layer 16 of the light redirecting layer 10 by the first protective layer 181.

Next, referring to fig. 6, a perspective view of a light redirecting film according to another preferred embodiment of the present invention is shown. As shown in fig. 6, the light redirecting film 10 is used as a protective film for the integrated polarizing film 19, the integrated polarizing film 19 includes a first protective layer 191 and a polarizing layer 192, and the light redirecting film 10 is adhered to the polarizing layer 192 of the integrated polarizing film 19 via the second layer 16, so that the light redirecting film 10 can be used as a protective film for the integrated polarizing film 19.

Example 1

The intermediate layer 14 of the light redirecting film 10 disclosed in this embodiment 1 includes a first grating surface 14a and a second grating surface 14b, and the first grating surface 14a and the second grating surface 14b are located on opposite sides, and a plurality of gratings 1-11 with different sizes are sequentially and periodically formed on the first grating surface 14a and the second grating surface 14b, respectively, as shown in the first table, wherein the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b have the same size and shape, except that the first grating 141 extends along a first direction D1, the second grating 142 extends along a second direction D2, and an intersecting angle between the first direction D1 and the second direction D2 is 90 ° ± 10 °. In addition, the refractive index of the first layer 12, the refractive index of the intermediate layer 14, and the refractive index of the second layer 16 in the light redirecting layer 10 were 1.5 and 1.6, respectively. The number of gratings on the first and second

grating surfaces

14a, 14b can be adjusted as desired, and after attaching the light redirecting film 10 to a liquid crystal display (model: hern 504K-C1(296H01), available from taiwan), Gamma values (Gamma values) at different horizontal and vertical viewing angles of the liquid crystal display are measured.

Table one: grating size on intermediate layer of light redirecting film

Example 2

The intermediate layer 14 of the light redirecting film 10 disclosed in this example 2 includes a first grating surface 14a and a second grating surface 14b, the first grating surface 14a and the second grating surface 14b are opposite to each other, and a plurality of gratings 1-11 with different sizes are sequentially and periodically formed on the first grating surface 14a, a plurality of gratings 12-20 with different sizes as shown in the second table are sequentially and periodically formed on the second grating surface 14b, wherein the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b have different sizes and shapes, and the first grating 141 extends along a first direction D1, the second grating 142 extends along the second direction D2, and the angle between the first direction D1 and the second direction D2 is 90 ° ± 10 °. In addition, the refractive index of the first layer 12, the refractive index of the intermediate layer 14, and the refractive index of the second layer 16 in the light redirecting layer 10 were 1.5 and 1.6, respectively. The number of gratings on the first and second

grating surfaces

14a, 14b can be adjusted as needed, and after the light redirecting film was attached to a liquid crystal display (model: HERAN504K-C1(296H01), available from Taiwan), Gamma values (Gamma values) at different horizontal and vertical viewing angles were measured.

Table two: grating size on intermediate layer of light redirecting film

Example 3

The intermediate layer 14 of the light redirecting film 10 disclosed in this embodiment 3 includes a first grating surface 14a and a second grating surface 14b, and the first grating surface 14a and the second grating surface 14b are located on opposite sides, and a plurality of gratings 12-20 with different sizes are sequentially and periodically formed on the first grating surface 14a and the second grating surface 14b, respectively, as shown in table two, wherein the first grating 141 on the first grating surface 14a and the second grating 142 on the second grating surface 14b have the same size and shape, except that the first grating 141 extends along a first direction D1, the second grating 142 extends along a second direction D2, and an intersecting angle between the first direction D1 and the second direction D2 is 90 ° ± 10 °. In addition, the refractive index of the first layer 12, the refractive index of the intermediate layer 14, and the refractive index of the second layer 16 in the light redirecting layer 10 were 1.5 and 1.6, respectively. The number of gratings on the first and second

grating surfaces

14a, 14b can be adjusted as required, and after the light redirecting film 10 is attached to a liquid crystal display (model: BenQ GW2270, available from Taiwan), the Gamma values (Gamma values) of the liquid crystal display at different horizontal and vertical viewing angles are measured.

Comparative example 1

A liquid crystal display (model: HERAN504K-C1(296H01), available from Taiwan) was used as comparative example 1, and the Gamma values (Gamma values) at different horizontal and vertical viewing angles of the liquid crystal display were measured without the light redirecting film of the present invention adhered thereto.

Comparative example 2

A liquid crystal display (model: BenQ GW2270, available from Taiwan) was used as comparative example 2, and the Gamma values (Gamma values) at different horizontal and vertical viewing angles of the liquid crystal display were measured without the light redirecting film of the present invention attached thereto.

Gamma value (Gamma value) is an indicator of the contrast and color saturation of a display, and a higher Gamma value indicates that the display provides the preferred contrast and color saturation.

The Gamma values (Gamma values) measured at different horizontal viewing angles for the liquid crystal displays of examples 1 to 3 incorporating the light redirecting film according to the present invention, and the Gamma values (Gamma values) measured at different horizontal viewing angles for the liquid crystal displays of comparative examples 1 to 2 not incorporating the light redirecting film according to the present invention are shown in the following table three:

table three: gamma value measured at different horizontal viewing angles

Horizontal viewing angle	0°	10°	20°	30°	40°	50°	60°	70°	80°
										Comparative example 1	2.24	2.03	1.71	1.44	1.23	1.07	0.94	0.87	0.87
Comparative example 2	2.33	2.28	2.08	1.82	1.62	1.32	0.99	0.70	0.73
										Example 1	1.81	1.74	1.60	1.43	1.27	1.13	1.02	0.96	0.99
Example 2	1.88	1.81	1.63	1.46	1.29	1.14	1.03	0.97	1.00
										Example 3	2.24	2.18	2.05	1.82	1.61	1.37	1.09	1.00	1.14

Examples 1-3, measured Gamma values at different vertical viewing angles for lcds equipped with the light redirecting film disclosed in the present invention, and comparative examples 1-2, measured Gamma values at different vertical viewing angles for lcds not equipped with the light redirecting film disclosed in the present invention, are shown in the following table four:

table four: gamma value measured at different vertical viewing angles

Vertical viewing angle	0°	10°	20°	30°	40°	50°	60°	70°	80°
										Comparative example 1	2.24	1.91	1.58	1.32	1.14	0.99	0.87	0.81	0.80
Comparative example 2	2.00	1.81	1.52	1.25	0.96	0.70	0.48	0.34	0.25
										Example 1	1.81	1.72	1.54	1.37	1.21	1.09	1.01	0.95	0.97
Example 2	1.88	1.77	1.57	1.38	1.23	1.12	1.03	0.96	0.96
										Example 3	2.24	2.14	1.89	1.64	1.37	1.08	0.82	0.84	0.84

According to the measurement results of examples 1-3 and comparative examples 1-2, compared to comparative example 1 in which the light redirecting film disclosed in the present invention is not used, the liquid crystal displays of examples 1 and 2 can improve the contrast and color saturation at a horizontal viewing angle of 40 ° to 80 ° and improve the contrast and color saturation at a vertical viewing angle of 30 ° to 80 ° by using the light redirecting film disclosed in the present invention. Compared with the comparative example 2 in which the light redirecting film disclosed by the invention is not used in the liquid crystal display, the liquid crystal display of the embodiment 3 can improve the contrast and the color saturation between the horizontal viewing angle of 50 degrees and 80 degrees and improve the contrast and the color saturation between the vertical viewing angle of 0 degrees and 80 degrees by adopting the light redirecting film disclosed by the invention. It is obvious that the present invention can actually improve the display quality of the liquid crystal display and is suitable for displays with different designs.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Description of the symbols

10 light redirecting film 14b second grating surface

12 first layer 141 first grating

14 intermediate layer 142 second grating

14a first grating surface 16 second layer

18. 19 polarizing film D2 second direction

181. 191 width of the first protective layer w1, w2

182. 192 polarizing layer d1, d2 depth

183 second protective layer g1, g2 spacing

D1 first direction

Claims

1. A light redirecting film comprising:

a first layer having a refractive index n 1;

a second layer having a refractive index n 3; and

an intermediate layer having a refractive index n2 sandwiched between the first layer and the second layer, the intermediate layer including a first grating surface having a plurality of first gratings extending in a first direction and a second grating surface having a plurality of second gratings extending in a second direction, the first direction intersecting the second direction at an angle of between 90 ° ± 10 °;

wherein the first grating surface of the intermediate layer is filled and planarized by the first layer, the second grating surface of the intermediate layer is filled and planarized by the second layer, and n2 is greater than n1, and n2 is greater than n 3.

2. The light redirecting film of claim 1, wherein the refractive indices n1, n2, and n3 are each between 1.4 and 1.7.

3. The light redirecting film of claim 2, wherein n1 is the same as or different from n 3.

4. The light redirecting film of claim 2, wherein the difference between n2 and n1 is not less than 0.1 and not greater than 0.3.

5. The light redirecting film of claim 2, wherein the difference between n2 and n3 is not less than 0.1 and not greater than 0.3.

6. The light redirecting film of claim 1, wherein each of the first gratings has a width w1, each of the second gratings has a width w2, and w1 and w2 are each independently between 0.3 μm and 1.5 μm.

7. The light redirecting film of claim 1, wherein each of the first gratings has a depth d1, each of the second gratings has a depth d2, and each of d1 and d2 is independently from 0.5 μm to 1.5 μm.

8. The light redirecting film of claim 1, wherein a spacing between two adjacent first gratings is g1, a spacing between two adjacent second gratings is g2, and g1 and g2 are each independently between 0.3 μm and 1.5 μm.

9. The light redirecting film of claim 1, wherein the width, depth, and spacing between each adjacent first grating and each adjacent second grating are the same or different.

10. The light redirecting film of claim 1, further comprising an optical film adhered to the light redirecting film, wherein the optical film is selected from the group consisting of a polarizing film, a hard coat film, a highly reflective film, an anti-glare film, and a protective film, or combinations thereof.